Organizations: National Natural Science Foundation of China (NSFC) [U1504510, U1604129, U1404619, 21173068]
Here, we present the investigations of photo-isomerization behavior and the nonlinear optical properties of azobenzene derivative LB films. The few-layer LB films of AOB-t4 and BNB-t4 exhibit positive nonlinear refraction and two-photon absorption properties as revealed by picosecond Z-scan. The increased conjugation by introducing an oxadiazole group improves the photo-isomerization rate and the nonlinear optical properties, due to a weaker intermolecular interaction and the formation of J-aggregates within AOB-t4 LB film. The third-order susceptibility of cis-AOB-t4 9-layer LB film reaches 1.866 x 10(-9) esu and the two-photon absorption coefficient is on the order of 10(-8) m/W. Interestingly, the 15-layer AOB-t4 LB film shows negative nonlinear refraction and saturable absorption. Taken together, we have demonstrated the switchable nonlinear optical absorption and refraction properties of AOB-t4 LB film with changing film thickness, which is of significance for nonlinear optics and photonics applications. (C) 2017 Optical Society of America
